Random misfire - engine misfiring?

Okay, I think I have a stuck valve and no idea how to free it.

Okay, I did a compression test both cylinders two and four were 150.

Did the rest of the cylinder 120 all around

I have a 2003 Nissan Frontier 4X4 6 cylinder truck. I keep getting a misfire in cylinder 2. This only happens when the engine has ran for 15+ mins or so, turned off for 5 mins, then I start it up again. The engine rumbles pretty bad for a few mins then it is fine again. I have changed the spark plugs/ wires, rotor/cap, oil and the fuel filter. Kinda stumped on this one. Any thoughts?

Changed the knock sensor in this vehicle. New gaskets, plugs, wires, cap and rotor. Put it back together. Checked for codes after first restart, all was good the computer had reset itself. Now after idling for about five minutes or so I can hear some type of knocking. Not sure if its coming from the supercharger or the valve train. However, the check engine light on the dash started flashing and when plugged into the OBD2 reader its giving me a code for cylinder 6 misfire. I pulled the plug and checked it had an extra wire so I changed it and same issue. Any ideas as to what I am possibly dealing with at this point?

First started with when accerlerating up hills, it would miss like hesitate to climb hill. Then got to where missing just after being started and would get worse even while driving. Had it checked a good time before got worse at advance auto, said it showed knock sensor and oxygen sensor. I already had a knock sensor so when it had got worse on the missing, my husband and dad are diy's and they replaced the knock sensor and also valve gasket because it also had oil leak, also replace manifold gasket, I think. After the truck was started it was smoking under the hood and from the exhaust. It wouldn't hardly run and even now won't hardly. My son drove to have another test done on it, he said the missing was worse than before and quit on him twice. Advance Auto said it showed a knock sensor circuit too high ( or something like that ) and an engine coolant sensor. Could you help? Thank you very much! If I could I may would give a donation, but my husband is waiting disability and have no idea when he could get it and our income is very low for a family of 5. Your help is greatly appreciated!

Just because a code says knock sensor in it doesn't mean the knock sensor is bad. Code readers donr tell u what part to change so having it read at a parts store isn't very helpful. If it says knock sensor circut high voltage it is an electrical problem check to make sure the plug is snapped tight on the sensor and look for breaks in wires leading to knock sensor. However it sounds like there is more then one problem

My Frontier idles ans run well until it hits about 45 then it run rough until it gets to 65 then it smooths out. It sets an error code of P301 - missfire cylinder 1. I have change the plugs, plug wire, distribute cap and rotor. I'm not sure what to try next. I thought maybe the coil but only cylinder 1 is giving be the code. Thanks for you help.

I got the same P301 code but the initial problem (without getting the error code) is that the car is loosing water/coolant without no leaking. After a week I got the P301 and I've checked the sparkplug from the cyl no. 1 and it has a green-like color, I think there is a coolant leak problem, am I right?

Thank you

Engine Performance problem
2002 Nissan Frontier 4 cyl Two Wheel Drive Automatic

I have an intermitent misfire code in cylinder 1. At areound 2k RPM it is noticible in how the engine performs. At that speed if I drop out of overdrive it is fine again. At idle no problem. At highway speed no problem. Lousy gas mileage. Local shop has replaced distributor, #1 injector, plugs, primary ignition wires etc. No change. Compression is ok.

Where do I look next?

Thanks.